update readme doc

Author: hathach

README.md

@@ -2,7 +2,17 @@
 
 [![Build Status](https://github.com/adafruit/Adafruit_nRF52_Bootloader/workflows/Build/badge.svg)](https://github.com/adafruit/Adafruit_nRF52_Bootloader/actions)
 
-This is a CDC/DFU/UF2 bootloader for nRF52 boards.
+A CDC/DFU/UF2 bootloader for Nordic nRF52 microcontroller. UF2 is an easy-to-use bootloader that appears as a flash drive. You can just copy `.uf2`-format application images to the flash drive to load new firmware. See https://github.com/Microsoft/uf2 for more information.
+
+DFU via serial/CDC requires [adafruit-nrfutil](https://github.com/adafruit/Adafruit_nRF52_nrfutil), a modified version of [Nordic nrfutil](https://github.com/NordicSemiconductor/pc-nrfutil). Install `python3` if it is not installed already and run this command to install adafruit-nrfutil from PyPi:
+
+```
+$ pip3 install --user adafruit-nrfutil
+```
+
+## Supported Boards
+
+Officially supported boards are:
 
 - [Adafruit CLUE](https://www.adafruit.com/product/4500)
 - [Adafruit Circuit Playground Bluefruit](https://www.adafruit.com/product/4333)
@@ -12,34 +22,9 @@ This is a CDC/DFU/UF2 bootloader for nRF52 boards.
 - [Adafruit ItsyBitsy nRF52840 Express](https://www.adafruit.com/product/4481)
 - [Adafruit LED Glasses Driver nRF52840](https://www.adafruit.com/product/5217)
 - Adafruit Metro nRF52840 Express
-- [Akizukidenshi AE-BL652-BO](https://akizukidenshi.com/catalog/g/gK-15567/)
-- [Electronut Labs Papyr](https://docs.electronut.in/papyr/)
-- [iLabs Challenger 840 BLE](https://ilabs.se/challenger-840-ble-datasheet/)
-- [MakerDiary MDK nRF52840 USB Dongle](https://makerdiary.com/products/nrf52840-mdk-usb-dongle)
-- [MakerDiary nRF52840 M.2 Module](https://makerdiary.com/products/nrf52840-m2-module)
-- [Nordic nRF52840DK PCA10056](https://www.nordicsemi.com/Software-and-Tools/Development-Kits/nRF52840-DK)
-- [Nordic nRF52840DK PCA10059 ("Dongle")](https://www.nordicsemi.com/Software-and-Tools/Development-Kits/nRF52840-Dongle)
-- Particle Argon
-- Particle Boron
-- Particle Xenon
-- [SparkFun MicroMod nRF52840](https://www.sparkfun.com/products/16984)
+- [Raytac MDBT50Q-RX Dongle](https://www.adafruit.com/product/5199)
 
-UF2 is an easy-to-use bootloader that appears as a flash drive. You can just copy `.uf2`-format
-application images to the flash drive to load new firmware. See https://github.com/Microsoft/uf2 and https://github.com/adafruit/uf2-samdx1 for more information.
-
-[adafruit-nrfutil](https://github.com/adafruit/Adafruit_nRF52_nrfutil), a modified version of [Nordic nrfutil](https://github.com/NordicSemiconductor/pc-nrfutil), is required to perform DFU. Install `python3` if it is not installed already and run this command to install adafruit-nrfutil from PyPi:
-
-```
-$ pip3 install --user adafruit-nrfutil
-```
-
-Clone this repo with following commands, or fork it for your own development
-
-```
-git clone https://github.com/adafruit/Adafruit_nRF52_Bootloader
-cd Adafruit_nRF52_Bootloader
-git submodule update --init
-```
+In addition, there is also lots of other 3rd-party boards which are added by other makers, users and community. Check out the [complete list of all boards here](/src/boards).
 
 ## Features
 
@@ -129,6 +114,16 @@ You must have have a J-Link available to "unbrick" your device.
 
 ### Build:
 
+Firstly clone this repo with following commands
+
+```
+git clone https://github.com/adafruit/Adafruit_nRF52_Bootloader
+cd Adafruit_nRF52_Bootloader
+git submodule update --init
+```
+
+Then build it with `make BOARD={board} all`, for example:
+
 ```
 make BOARD=feather_nrf52840_express all
 ```